The preparation of highly unsaturated polyethers having repeating units possessing the general configuration ##STR2## is known wherein a polyepichlorohydrin is dehydrohalogenated. Numerous methods can be utilized to effect the vigorous dehydrohalogenating conditions. These include the use of strong bases, high temperatures or different types of solvents or combinations of two or more of these techniques. The dehydrohalogenation may be effected, for example, by heating the previously prepared polyepihalohydrin with sodium methoxide in methanol, tetrahydrofuran or dimethylsulfoxide under reflux.
In order to effect the dehydrohalogenation and still retain the hydroxyl group or groups or epoxy groups in the terminal units so that they may be present for subsequent reaction, it has been found most helpful to effect the reaction in the presence of dimethyl sulfoxide or tetrahydrofuran as the solvent and metal alkoxides such as sodium methoxide as dehydrohalogenating agents.
It is also known to make valuable high energy adducts from these polyethers by reacting them with N.sub.2 F.sub.4 under conditions so as to obtain the maximum conversion of double bonds to vicinal bis(difluoramino) groups. The usual and preferred method comprises adding N.sub.2 F.sub.4 gas to a reactor containing the functional polyunsaturated polymer in a suitable solvent at elevated temperatures and pressures. The resulting polymer contains high energy groups which comprises a polyether having repeating units of ##STR3## WHEREIN R is hydrogen or a lower alkyl such as methyl or ethyl, preferably hydrogen, and n is an integer between about 10 and 60.
While these difluoroamino-containing polymers do exhibit high energy characteristics that make them especially useful as propellant binders, they do not have the necessary stability required for use in high-temperature binders. In other words, at high temperatures, i.e., above 100.degree. C, they tend to decompose to liberate gaseous by-products. Accordingly these polymers are unsuitable as propellant binders for some applications.
It has now been found that novel, stable, high-energy binders are obtained when these difluoroamino-containing polymers are reacted with suitable basic compounds. The resulting polyethers have repeating units ##STR4## wherein R is hydrogen or a lower alkyl, and are significantly more stable than the difluoramino-containing polyether precursor yet retain high-energy characteristics.
The preparation of suitable polyepihalohydrins, their dehydrohalogenation, and their conversion to polyethers by reaction with N.sub.2 F.sub.4 is adequately described in detail in related copending patent applications Ser. No. 423,646, filed Dec. 31, 1964, now U.S. Pat. No. 3,976,602, issued Aug. 24, 1976; Ser. No. 660,546, filed July 12, 1967, now U.S. Pat. No. 3,875,189, issued Apr. 1, 1975; and Ser. No. 660,545, filed July 12, 1967, now U.S. Pat. No. 3,914,209, issued Oct. 21, 1975.